This application claims the priority of Korean Patent Application No. 2003-98228, filed on Dec. 27, 2003, which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a light emitting device and a method of manufacturing the same. More particularly it relates to an organic light emitting device and a method of manufacturing the same.
2. Description of the Related Art
Top emitting light emitting devices may have superior light emitting efficiency compared to bottom emitting light emitting devices. Thus, the top emitting light emitting devices are more widely used for displays.
A conventional top emitting light emitting device, as illustrated in FIG. 1, can include a cathode layer 10, a light emitting layer 12 that emits light L, a hole transport layer 14, and an anode layer 16 formed sequentially. The anode layer 16 can be an indium tin oxide (ITO) layer, which is a conductive and transparent layer.
The ITO layer is deposited at a high temperature, and also subject to heat treatment to enhance conductivity. The deposition and heat treatment of the ITO layer are typically performed at a temperature of 400° C. or greater. However, light emitting material may not withstand such a the high temperature deposition process and the heat treatment process.
Thus, a method of depositing an ITO layer at a low temperature has been developed. However, when the ITO layer is deposited at a low temperature, the performance of the light emitting device degrades because the ITO layer breaks off. Accordingly, the desired result has not been obtained.
In addition, a conventional light emitting device has low out coupling efficiency. Out coupling efficiency is a measure of the amount of transmitted light compared to that amount plus the amount lost to total internal reflection. That is, light reflected from a boundary of elements having different reflective indices within an organic light emitting device can be reflected back inside the organic light emitting device.
This reflected light can be either substantially parallel to the substrate or substantially perpendicular to the substrate. Most of the light parallel to the substrate is emitted from the corners of the substrate. The light perpendicular to the substrate can be emitted to the desired direction by using a reflection layer on the opposite side from the substrate. The reflection layer can be formed separately from the anode layer.
However, of the initially reflected light from a boundary of elements, the light that is parallel to the substrate and leaks out of the organic light emitting device can be almost 50% of the total leakage light of the organic light emitting device. Therefore, the luminous efficiency is lower than desired.